Rail vehicles, such as a train having one or more locomotives, for example, travel along a route from one location to another. Some trains travel along the route in an automatic mode in which, prior to traveling along the route, a controller predetermines one or more train parameters, such as speed and notch setting, for example, at each location along the route. In order to predetermine the train parameter(s) at each location along the route, the controller may use a memory which prestores a characteristic of the route at each location, such as the grade, for example. While traveling along the route, the controller may need to be aware of the train location to ensure that actual train parameter(s) track or match the predetermined train parameter(s) at each train location. Additionally, since the route may include various train parameter restrictions at various locations, such as a speed restriction, for example, the controller may need to be aware when the train location is approaching a location of a restriction in order to adjust the train parameter(s), if needed, to comply with the train parameter restriction.
Alternatively, the train may travel along the route in a manual mode, in which the train operator is responsible for manually adjusting the train parameters. As with the automatic mode, while traveling along the route, the train operator may need to be aware of the train location, such as when the train location approaches a restriction location, for example. The train operator can then manually adjust the train parameter(s) to comply with a train parameter restriction.
Some known systems have been designed to assist the controllers in the automatic mode and the train operators in the manual mode by providing locations of the train as the train travels along the route. These systems, however, may rely solely on a global positioning satellite (GPS) system, which provides one measurement of the train location based on satellite positioning, or other positioning systems using wireless network or wayside equipment, to provide raw position measurements of the train. Upon receiving the positioning system measurement, the controller uses an internal memory to convert this raw position measurement to a distance measurement of the train along the route.
As with any measurement system, such position measurement systems are capable of error, such as if a GPS receiver of the train fails to communicate with a sufficient number of satellites in the GPS system or an error in the memory of the controller which may convert an accurate raw position measurement to an inaccurate distance measurement along the route, for example. Accordingly, it would be advantageous to provide plural independent distance measurements, such as an independent distance or position measurement in addition to a GPS measurement of the distance of the train along the route, so to ensure that the distance estimation provided to the controller or train operator is reliable. Additionally, it would be advantageous to assign a quality value to the distance estimation provided to the controller or train operator.